The present invention relates to the general field of optical detectors for determining the position of an object on a substantially plane surface. The object can in particular have various geometrical and/or optical characteristics, in particular various shapes and/or colors.
The invention can be applied in particular in the field of data entry, for example alphanumeric data entry. The invention therefore finds an application in the production of keyboards or similar devices for manual data entry, such as computers, telephones, personal digital assistants, etc.
Various optical devices are known for detecting the position of an object with a view to entering data.
One standard technique for position determination in two dimensions produces a grid of emitter/receiver pairs and determines the position of the object from which beams are cut. Relying on transmission, that kind of technique offers little flexibility and requires the use of numerous components.
Another solution, described in the document FR 2 826 443, is to place emitters and receivers on two facing opposite sides of a surface. That reduces the number of components but it is still necessary to provide connection members between the two opposite sides of the active surface, which is still limited by the geometry of the device.
The document FR 2 859 277 describes a method of determining the position of an object based on reflection by the object of light emitted by one or more emitters, the reflected light being detected by one or more receivers and then analyzed to determine the position of the object.
The emitters and receivers alternate in the same row, which makes the active surface less dependent on the geometry of the device. Among other things, this makes integration very flexible. The position of an object on a substantially plane surface can then be determined to enable an operator to enter data in a similar way to entry via a keyboard.
Devices using that method enable data to be entered but they are often lacking in flexibility and accuracy.
This is reflected either in requiring many attempts to enter information or in the device having a relatively long response time. Overall, it has been found that that kind of method regularly causes a loss of time that prejudices the application of the method in fields where entry time is an important parameter.